Refractive outcome after myopic Refractive outcome after myopic LASIK with a mechanical LASIK with a mechanical

microkeratome or a femtosecond microkeratome or a femtosecond laser keratome laser keratome

Mark E Johnston, MD, FRCSCMark E Johnston, MD, FRCSC

www.nebraskaeye.comwww.nebraskaeye.com

No financial interests in any No financial interests in any productproduct

Purpose:Purpose:

An increased number of myopic An increased number of myopic enhancements were noted following Lasik enhancements were noted following Lasik with a femtosecond keratomewith a femtosecond keratome. .

This study was undertaken to refine our This study was undertaken to refine our nomogram; particularly to differentiate nomogram; particularly to differentiate between between – low myopia vs high myopia low myopia vs high myopia

spherical equivalent under/over -6.00 Dioptersspherical equivalent under/over -6.00 Diopters

– younger vs older patients younger vs older patients under / over age 40under / over age 40

Central island and undercorrection Central island and undercorrection with IntraLasewith IntraLase

Corneal incisions can create a Corneal incisions can create a myopic refractive errormyopic refractive error

Corneal flattening by shallow circular Corneal flattening by shallow circular trephination in human eye bank eyes.trephination in human eye bank eyes.Gilbert MLGilbert ML, , Roth ASRoth AS, , Friedlander MHFriedlander MH..Refract Corneal Surg. 1990 Mar-Apr;6(2):113-6. Refract Corneal Surg. 1990 Mar-Apr;6(2):113-6.

The mean acute central The mean acute central keratometric flattening from the keratometric flattening from the shallow trephine incision was shallow trephine incision was 2.81 D (SD 2.28, P = .017)2.81 D (SD 2.28, P = .017)

Clinical: Edge profileClinical: Edge profileMicrokeratome: Microkeratome:

Stepped / beveledStepped / beveled

IntraLase:IntraLase:

Sharp edge / steepSharp edge / steep

METHODS:METHODS:

Lasik flaps were made with a Zyoptix XP microkeratome® 140 Lasik flaps were made with a Zyoptix XP microkeratome® 140 micron blade (MK) or IntraLase® 130 micron (IL). micron blade (MK) or IntraLase® 130 micron (IL). VISX® wavefront guided ablations were done. VISX® wavefront guided ablations were done. During the study period we treated 1081 eyes in the During the study period we treated 1081 eyes in the microkeratome group and 644 eyes in the IntraLase group.microkeratome group and 644 eyes in the IntraLase group.Small target adjustments were made for age, spherical Small target adjustments were made for age, spherical aberration and cylinder. aberration and cylinder. IntraLase was done if preferred by the patient or when IntraLase was done if preferred by the patient or when recommended by the surgeon, most commonly older patients recommended by the surgeon, most commonly older patients (over 40) and patients with higher corrections. (over 40) and patients with higher corrections. The Refractive Surgical Consultant® was used to analyze all The Refractive Surgical Consultant® was used to analyze all available results at one, three and six months after surgery.available results at one, three and six months after surgery.Statistical analysis was done with two-tailed p value, statistical Statistical analysis was done with two-tailed p value, statistical significance at p<0.05.significance at p<0.05.

Results: Results: Difference between spherical equivalent (SE) outcome and Difference between spherical equivalent (SE) outcome and

predicted SE outcome with standard deviation (SD)predicted SE outcome with standard deviation (SD)

Zyoptix XP IntraLase P value

Sph Eq St Dev # Sph Eq St Dev #

All patients

1 mo -0.05 0.41 915 -0.14 0.48 521 0.0002

3mo -0.12 0.44 411 -0.21 0.52 292 0.0135

6mo -0.16 0.43 333 -0.28 0.55 248 0.0035

*The subsets of under/over age 40 with low myopia showed similar trends

High myopia & under 40

1 mo +0.08 0.52 56 -0.29 0.59 63 0.0005

3 mo -0.04 0.80 23 -0.45 0.59 29 0.0384

6 mo -0.13 0.50 22 -0.55 0.90 32 0.0589^*There were an insufficient number of cases in the over 40/high myopia subset for clinical significance^Borderline statistically significant

Clinical observationsClinical observationsHansatome: Gutter usually Hansatome: Gutter usually only visible with manipulation only visible with manipulation

Intralase: Gutter usually Intralase: Gutter usually visible with the microscopevisible with the microscope

IntraLase gutter :IntraLase gutter :depressed scar with pooling of depressed scar with pooling of

stain stain

Myopic shift: Zyoptix XP vs IntraLase

Microkeratome

Zyoptix XP vs IntraLase:Zyoptix XP vs IntraLase:over age 40, high myopia*over age 40, high myopia*

Initial study with additional cases for 6 months : P=0.0071Initial study with additional cases for 6 months : P=0.0071( The initial study had an insufficient number of cases in the over 40 / high myopia subset( The initial study had an insufficient number of cases in the over 40 / high myopia subset

for statistical significance)for statistical significance)

+0.24 +/- 0.51 -0.14 +/- 0.71

IntraLaseMicrokeratome

Conclusion:Conclusion:

When compared to the Zyoptix XP When compared to the Zyoptix XP microkeratome, IntraLase is associated microkeratome, IntraLase is associated with a greater average myopic shift and a with a greater average myopic shift and a higher standard deviation. Using these higher standard deviation. Using these results, adjustments have been made to results, adjustments have been made to our treatment nomogram, especially for our treatment nomogram, especially for patientspatients withwith higher correctionshigher corrections